A common practice in forming fibers of mineral material such as glass fibers, is to discharge the molten glass into a rotating centrifuge or spinner. A spinner typically has an orificed peripheral wall, and molten glass flows radially outwardly on the spinner bottom wall, upward along the spinner peripheral wall, and finally passes through the orifices to produce glass fibers. Typically, the spinner peripheral wall is adapted with 12,000 or more orifices, having a diameter within the range of from about 20 to about 40 thousandths inches. The streams of glass emanating from the spinner are rapidly cooled from an initial temperature on the order of about 1800.degree. F. to room temperature.
One of the problems associated with centrifuging fibers is that of controlling the characteristics, both chemical and physical, of the material immediately prior to fiberization. It would be desirable, for example, if one were able to modify the viscosity or chemical composition of the material immediately prior to fiberization. The last minute addition of certain chemicals to the material could help avoid pollution problems. The last minute addition could also be used to control the composition and characteristics of the material where the introduction of a substance into molten material generates a fast-paced chemical or physical reaction. It is desirable to control composition and characteristics not only of mineral fibers, but also of ceramic, polymeric and other organic fibers.
Another long sought objective of fiber forming processes is the ability to control the environment of the stream of molten material issuing from the orifices of the spinner or bushing. Molten streams of glass, for example, are subject to significant attenuation forces in an environment of turbulent gases of varying temperature and chemical composition prior to the solidification of the streams into solid fibers. It would be desirable to have better control of the environment experienced by the molten streams as they issue from the centrifuge or bushing.
Another desirable attribute of fiber forming processes is the ability to manufacture hollow or partially hollow fibers. Such fibers would enable weight reduction and improve the thermal resistance of insulation products.